#include<fstream>
using namespace std;
int k[1000000];
int main(){
	int n,i,j;
	long long s=0;
	ifstream in("fractii.in");
	in>>n;
	in.close();
	for(i=1;i<=n;i++)
		k[i]=i;
	for(i=2;i<=n;i++){
		if(k[i]==i)
			for(j=i;j<=n;j+=i){
				k[j]/=i;
				k[j]*=i-1;
				}
		s+=k[i];
		}
	ofstream out("fractii.out");
	out<<s*2+1;
	out.close();
	return 0;
	}